Series 2 keeps blowing overdrive fuse

[S2Alan]

Hi Everyone, new to the club and forum.

I have a 1978 xj series 2 4.2 manual with overdrive and recently it blew the overdrive/instrument fuse when I was driving back home.
I did a basic wiring/switch check and I can get the overdrive solenoid to click when stationary with engine off in 4th but as soon as I drive it, it blows the fuse straight away, I'm wandering if I could have a solenoid fault or worse case a fault within the overdrive unit. Has anyone had any similar issues.
Any pointers in a right direction would be appreciated.

Regards
Alan

[oldtimer]

Alan,
I have recently responded to an overdrive problem on a Mk 2 please try and find it and have a read.

My initial thinking is that it may just be solenoid adjustment required.

Do come back I'm sure we can work through this

[S2Alan]

Well I had a brief look again today and found that the solenoid was slightly loose, I tightened it and took for another run and hey presto it worked fine for about 4 miles and then it popped the fuse again.! Ive now removed the solenoid and checked it out, I left the plunger attached to the overdrive as I was running low on time and noticed that it has a flat on one side, is this normal??
Ive now refitted it and it now works ok but ive not ran it for long, I think it may have a dodgy solenoid??

[oldtimer]

Alan.
Did you manage to find my post ref Mk 2 overdrive and have a read. that will help me not having to repeat myself.

[S2Alan]

I did have a look but had no luck finding it sadly.

[PaulGover]

I presume oldtimer means one of the following posts
Re: Relay for the overdrive?
Re: Help please re. gearbox with overdrive
Re: Overdrive interchangeability